Even so, I think 10-12 response options on any character is too many. There is such a thing as having too many choices, after all.

If these responses are there just for roleplaying purposes, to provide the player with different ways of saying the same thing, there's really only so much you can do here. For the fussy roleplayer who would value such a thing, you'll probably never list exactly what they want to say, anyhow. The other option is to not put any voice in at all (such as [tell him to go away]) which is, in my opinion, sacrificing all character for everyone.
Generally we stick with distinct "voices" for the player: the goody two-shoes, the evil bastard, the smart-*** rogue, the neutral mercenary ...but even then, you're not going to use every voice in every situation unless they're saying very different things.

If these responses are there to provide different means of solving problems, that's fine... and, indeed, we've been working on including more and more of that. You have to keep in mind, however, that each solution is something you're going to have to follow through with on the consequences in terms of design and scripting. So you can only provide as many options as you have time for, and even then you have to keep them simple.